首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the qualit
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the qualit
admin
2015-07-13
60
问题
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the quality of their wood. Genetically-engineered food crops have become increasingly common, albeit controversial, over the past ten years. But genetic engineering of trees has lagged behind.
Part of the reason is technical. Understanding, and then altering, the genes of a big pine tree are more complex than creating a better tomato. While tomatoes sprout happily, and rapidly, in the laboratory, growing a whole tree from a single, genetically altered cell in a test tube is a tricky process that takes years, not months. Moreover, little is known about tree genes. Some trees, such as pine trees, have a lot of DNA—roughly ten times as much as human. And, whereas the Human Genome Project is more than halfway through its task of isolating and sequencing the estimated 100,000 genes in human cells, similar efforts to analyze tree genes are still just saplings.
Given the large number of tree genes and the little that is known about them, tree engineers are starting with a search for genetic "markers". The first step is to isolate DNA from trees with desirable properties such as insect resistance. The next step is to find stretches of DNA that show the presence of a particular gene. Then, when you mate two trees with different desirable properties, it is simple to check which offspring contain them all by looking for the genetic markers. Henry Amerson, at North Carolina State University, is using genetic markers to breed fungal resistance into southern pines. Billions of these are grown across America for pulp and paper, and outbreaks of disease are expensive. But not all individual trees are susceptible. Dr. Amerson’s group has found markers that distinguish fungus-resistant stock from disease-prone trees. Using traditional breeding techniques, they are introducing the resistance genes into pines on test sites in America.
Using genetic markers speeds up old-fashioned breeding methods because you no longer have to wait for the tree to grow up to see if it has the desired traits. But it is more a sophisticated form of selective breeding. Now, however, interest in genetic tinkering is also gaining ground. To this end, Dr. Amerson and his colleagues are taking part in the Pine Gene Discovery Project, an initiative to identify and sequence the 50,000-odd genes in the pine tree’s genome. Knowing which gene does what should make it easier to know what to alter.
Compared with genetic engineering of food crops, genetic engineering of trees _____.
选项
A、began much later
B、has developed more slowly
C、is less useful
D、is less controversial
答案
B
解析
事实细节题。由题干中的genetic engineering of trees可定位到第一段最后一句。本文并没有提到树木基因改良技术从什么时候开始,所以有可能树木的基因改良技术和别的基因改良技术在开始的时间上相差不大,但在所取得的成果方面却有很大的差别,因此,本题关键在于理解第一段最后一句中的lag behind指的是程度上的落后,而非时间上的落后,故B项正确。
转载请注明原文地址:https://kaotiyun.com/show/C074777K
0
考研英语一
相关试题推荐
WildelephantsroamacrossthecrowdedplainsofIndia;forestedriverbankswindthroughcattleranchesinBrazil;aribbonof
Educationisoneofthekeywordsofourtime.Aman,withoutaneducation,manyofusbelieve,isanunfortunatevictimofunfo
[A]Whattodoasastudent?[B]Variousdefinitionsofplagiarism.[C]Ideasshouldalwaysbesourced.[D]Ignorancecanbeforgive
TheAmericaneconomyisgrowing,accordingtothemostrecentstatistics,atthehighrateof7%,andisinthemiddleofthel
TotakethegraduateentranceexaminationofPekingUniversity,you’dbetterbuysomerelatedexaminationpaperfromtheGraduat
Forcenturies,explorershaveriskedtheirlivesventuringintotheunknownforreasonsthatweretovaryingdegreeseconomican
Thequestioningoftheroleofthepublicgalleryisnotanewphenomenon.Itissomethingthathasbeenarguedoversinceitsv
Howcanacompanyimproveitssales?Oneofthekeystomoreeffectivesellingisforacompanytofirstdecideonits"salesst
YouwillgraduatefromuniversityandintendtobeavolunteertogototheWestofChina.Afterreadinganoticeofrecruitment
Doanimalshaverights?Thisishowthequestionisusuallyput.Itsoundslikeauseful,groundclearingwaytostart.(46)Actu
随机试题
Friendsplayanimportantpartinourlives,andalthoughwemaytakethefriendshipforgranted,weoftendon’tclearlyunders
中链脂肪酸的碳链含碳原子数为()。
A.利水消肿B.益气复脉C.健脾补肾D.益气生津E.健脾宁心参芪降糖胶囊除益气养阴外,还能()。
以血清肌酐法制订个体化给药方案的依据是
1997年5月2日,卢某因协助外国人进入我国国境,被主管机关处以5日拘留。按照《行政处罚法》的规定,这项处罚应当由哪种规范性文件设定?
________是规划渐进明晰的一种表现形式,近期要完成的工作在工作分解结构最下层详细规划,而计划在远期完成的工作分解结构组成部分的工作,在工作分解结构较高层规划。
什么是复述策略?试阐述常用的复述策略。
胆汁质的人性格开朗、热情、坦率、精力旺盛、反应速度快;抑郁质的人敏感、遇事优柔寡断、胆小怕事、性格孤僻、不善于交往。这说明人的气质是有好坏之分的。
Friendisbetterthanfortune.Friendisworsethanpoisoninsome【C1】______.Theabovetwostatementsareoppositeandseemt
ToswimacrosstheEnglishChanneltakesatleastninehours.It’sahardworkanditmakesyoushortofbreath.Toflyoverthe
最新回复
(
0
)